Aircraft flap extension mechanism

ABSTRACT

An aircraft mechanism including a flap positioning mechanism comprising a carriage and track system suitable for use with variable radius or multiple curvature tracks.

This application is the US national phase of international applicationPCT/GB01/04984 filed 13 Nov. 2001, which designated the US.

The present invention relates to an aircraft flap and is particularlyconcerned with an aircraft leading or trailing edge flap deploymentmechanism.

Most modern aircraft have a wing section that is optimised to producelow drag at cruising speed. In most cases such an optimised wing sectionwill not provide the high lift capability required during the take-offand landing phases of flight. Flap systems are used to provide the highlift capability required and these effectively increase the camber andsometimes the area of the wing when the flap is deployed. During thetake-off phase of flight the requirement is for high lift capabilitywith minimal increase in drag, whilst in the landing phase therequirement is for high lift capability and drag inducement in order toreduce the forward speed of the aircraft. Flaps may also be deployed inother phases of flight to increase lift.

Each phase of flight may require different flap settings. The geometricvariables controlled by deployment of the flap are:

-   -   Lap—the overlap between the wing and the flap    -   Gap—the gap between the leading or trailing edge of the wing and        the nearest point of the flap    -   Deployment angle—the angle between a horizontal reference and a        chord line of the flap.

A mechanism is required that will position a flap in order to achievethe correct lap, gap and deployment angle settings. Many such mechanismsrely on a track system to provide translational movement of the flap inwhich the flap is mounted on a carriage for rolling movement along atrack. The track is of constant thickness and has opposed rollingsurfaces thereon and the carriage is movable along the track on at leasttwo pairs of rollers, each pair of rollers having one roller running oneach opposed rolling surface and the rollers in each pair beingmaintained at a separation from one another, usually by a rigidconnecting link, whereby to maintain both rollers in rolling contactwith their respective track rolling surfaces at all times. The carriageis thus allowed to move smoothly along the track and to deploy the flapas required. Many different constant radius track profiles can beproduced for a three position system. However, there is only onecombination of carriage pivot offset from the flap surface, and anoffset along the chordwise axial flap that will generate a straight linetrack. Other combinations generate a constant radius track profile,however, in many cases it becomes necessary to modify these trackprofiles owing to:

-   -   A foul of the flap structure with other wing structure owing to        the arc the pivot point moves through and the path the flap thus        takes.    -   The loads on the flap mechanism are too great to allow a        feasible design to be produced owing to the carriage pivot point        being too far away from the line of action of the applied        aerodynamic load. Designing a track based mechanism to withstand        these loads would in all probability require a mechanism that        would be unacceptably heavy and large.    -   The flap mechanism should desirably be contained within the wing        box. Many possible constant radius track profile mechanisms,        especially of thin wing sections, are not contained by the wing        box.

Such modified track profiles have a variable radius or multiplecurvature track, often having a flattened ‘S’ shape profile. Existingsingle carriage track systems are only viable for either a constantradius or linear track profile as the sets of rollers will not otherwisebe able to maintain freely rotatable movement along the track.

Currently where constant radius tracks are not suitable other, morecomplex mechanisms are used. One such mechanism utilises a track havingfirst and second straight sections (sections of infinite radius)connected by a section of track having constant radius. First and secondcarriages are linked together and mounted on sets of rollers, each ofthe sets of rollers having a roller in contact with one of two opposedrolling surfaces of the track, each pair of rollers connected by a linkor arm. The rollers are positioned on the track to be freely rotatablealong the track at all times. The second carriage has a single pair ofrollers. The carriages are pivotally connected to the flap, the pivotalconnection of the second carriage being further aft than that of thesaid first carriage. The carriages both move along the said firstsection of infinite radius track. At the end of the first section ofinfinite radius track, the first carriage stops whilst the secondcarriage is free to move along the constant radius section of track andthe second section of infinite radius track. Thus at the end of thefirst section of infinite radius track, the pivotal connection of thefirst carriage is fixed in position and acts as a pivot point for theflap as the flap is moved into position by the second carriage movingalong the constant radius section and the second section of infiniteradius track. It will be appreciated by the reader that the abovedescribed mechanism is more complex than the single carriage mechanism.Also it is not always possible to design feasible mechanisms asdescribed above for the required flap deployment settings.

An object of the present invention is to produce a simpler flapdeployment mechanism suitable for use with a track of variable radiusprofile (multiple curvature).

According to a first aspect of the present invention there is providedan aircraft flap arrangement in which the flap is deployable between afirst stowed, or “cruise” position and a second deployed position, thedeployment movement including translational movement of the flap forwhich the flap is mounted on a carriage for rolling movement along atrack, the track having opposed rolling surfaces thereon and thecarriage being movable along the track on at least two pairs of rollers,each pair of rollers having one roller running on each opposed rollingsurface and the rollers in each pair being linked by a connecting meansthat maintains the roller in each pair of rollers at a fixed distanceapart in use, the connecting means is pivotally mounted to the carriagesuch that when the track is of multiple curvature the connecting meanspivots about the carriage maintaining both said rollers in each saidpair of rollers in rolling contact with their respective track rollingsurface at all times.

The connecting means preferably comprises means to articulate at leastone roller in the said at least one pair about an articulation axisspaced from the rolling axis of the said roller whereby a lineconnecting the rolling axes of the pair of rollers will pass throughboth points of contact of the rollers with the track.

The articulation axis is preferably equidistant between the rolling axesof the rollers in the said pair and the pivotal connection of the set ofrollers to the carriage will enable the rollers to freely rotate alongtracks of different profiles including tracks with variable radiusprofiles, including S-shaped profiles, whilst maintaining rollingcontact with the surface of the track. This will ensure the correctposition and orientation of the carriage and therefore the flap.

It is further preferred that at least one of the pairs of rollerscomprises an adjustment means to allow the distance between the rollersto be adjusted. The adjustment means will help minimise wear and allowthe carriage to be adjusted to take account of any initial tolerances inthe system. There may be said adjustment means on all of the pairs ofrollers. The adjustment means may conveniently be a cam style adjuster.

An alternative embodiment may include roller displacement means whichcomprises means to separate the two rollers in a given pair by an amountdependent upon the degree of curvature change of the track experiencedby that pair of rollers.

Thus the said pair of rollers may have a sensor or guide in contact withthe track immediately adjacent the wheels in that pair which sensescurvature changes in the track as the carriage moves along and, by amechanical or other, for example electrical, connection causes the saiddependent separation movement of the pair of rollers.

According to a second aspect of the present invention there is providedan aircraft wing having a flap deployment mechanism according to thefirst aspect of the present invention.

According to a third aspect of the present invention there is providedan aircraft having a wing according to the second aspect of the presentinvention.

A preferred embodiment of the present invention will now be described byway of example only and with reference to the accompanying drawings inwhich:

FIG. 1 is a diagramatical representation of a flap and deploymentarrangement or mechanism according to the invention showing thegeometric relationships between the ring, the flap and the flapdeployment mechanism;

FIG. 2 a is a diagramatical representation of the flap and deploymentmechanism at FIG. 1 shown in its stowed position;

FIG. 2 b is a diagramatical representation of the flap and deploymentmechanism of FIG. 1 shown in a deployed take-off position;

FIG. 2 c is a diagramatical representation of the flap and deploymentmechanism of FIG. 1 shown in a deployed landing position;

FIG. 3 shows a partial cross-section through a carriage according to oneembodiment of the present invention;

FIG. 4 shows a cross-section of FIG. 3 through the line A—A to anenlarged scale;

Referring firstly to FIG. 1 there is shown a flap 10 deployed from awing 20 by a flap deployment mechanism 30 comprising a double sidedtrack 40 and a carriage 50 moved by a drive system 60. The exact flapdeployment is determined by several geometric relationships set up togive the correct aerodynamic performance and characteristics of the flap10. The relevant geometric relationships are an overlap distance of thewing 20 and flap 10, measured longitudinally of the aircraft, and knownas the lap 70, a gap between the trailing edge of the wing 65 and thenearest point of the flap 10, known as the gap 80 and an angle α betweenthe horizontal reference 100 and a chordline 110 of the flap 10. Themain cause of loading on the carriage 50 is owing to the aerodynamicload 120 on the flap 10. To minimise the loading on the carriage 50 apivotal connection 130 of the carriage should be kept as close to theline of action of the applied aerodynamic load 120 as possible. Thepivotal connection 130 should not be outboard of the line of action ofthe applied aerodynamic load 120 at any time. If the pivotal connection130 were to be outboard of the aerodynamic load 120, any moment causedby the aerodynamic load 120 would tend to further deploy the flap 10.

FIGS. 2 a, 2 b and 2 c show typical flap deployment positions for athree position system. FIG. 2 a shows a stowed position, FIG. 2 b showsa take-off position and FIG. 2 c shows a landing position. In all threeFigures the positions of the flap 10, the carriage 50 and its pivotalconnection 130 and the direction of the aerodynamic load 120 are shown.FIGS. 2 b and 2 c also show the gap between the wing trailing edge 65and the closest point of the flap 10.

FIG. 3 shows one design of carriage 50 according to the presentinvention on a track 40. The carriage comprises a carriage body 55 and apivotal flap connection 160 and rollers 170. The rollers 170 disposed onopposed rolling surfaces 200, 210 of the track 40 are connected by anarm 180. A roller pair articulated axis 190 at a pivotal connection ofthe carriage 50 and the arm 180 allows the carriage 50 to pivot as therollers move over a variable radius track so that the rollers 170 areable to freely rotate at all times.

Referring to FIG. 4, there is shown a cross-section of the carriage 50and track 40 and one set of rollers 170 with their axles 200. The rollerarticulaltion connection 190 pivotally connects the carriage 50 to thearm 180 and allows the rollers to freely rotate as the carriage 50 movesalong a variable radius track.

1. A flap deployment mechanism for an aircraft flap arrangement in whichthe flap is deployable between a first stowed, or “cruise” position anda second deployed position, the deployment movement includingtranslational movement of the flap for which the flap is mounted on acarriage for rolling movement along a track, the track having opposedrolling surfaces thereon and the carriage being movable along the trackon at least two pairs of rollers, each pair of rollers having one rollerrunning on each opposed rolling surface and the rollers in each pairbeing linked by a connecting means that maintains the roller in eachpair of rollers at a fixed distance apart in use, the connecting meansis pivotally mounted to the carriage such that when the track is ofmultiple curvature the connecting means pivots about the carriagemaintaining both said rollers in each said pair of rollers in rollingcontact with their respective track rolling surface at all times.
 2. Aflap deployment mechanism as claimed in claim 1 wherein the track systemhas a variable radius profile.
 3. A flap deployment mechanism as claimedin claim 2 wherein the track system has an “S” shaped profile.
 4. A flapdeployment mechanism as claimed in claim 1 wherein each of the at leasttwo pairs of rollers comprises an adjustment means to allow the distancebetween the said rollers disposed on opposite sides of the track to beadjusted.
 5. A flap deployment mechanism as claimed in claim 4 whereineach of the pairs of rollers comprises said adjustment means.
 6. A flapdeployment mechanism as claimed in claim 4 wherein the adjustment meansis a cam style adjuster.
 7. An aircraft wing having a flap deploymentmechanism according to claim
 1. 8. An aircraft having a wing accordingto claim
 7. 9. A flap deployment mechanism for an aircraft flaparrangement in which the flap is deployable between a first stowed, or“cruise” position and a second deployed position, the deploymentmechanism comprising: a single track having opposed rolling surfacesthereon; a carriage with said flap mounted on said carriage, thecarriage including at least two pairs of rollers for rolling along saidrolling surfaces of said single track causing translational movement ofthe flap, each pair of rollers having one roller running on each opposedrolling surface; connecting means for linking the rollers in each pair,said connecting means maintaining the rollers in each pair of rollers afixed distance apart; and means for pivotally mounting the connectingmeans to the carriage wherein the connecting means pivots about thecarriage maintaining both said rollers in each said pair of rollers inrolling contact with their respective track rolling surface at all timesduring deployment movement.
 10. A flap deployment mechanism as claimedin claim 9 wherein the track system has a variable radius profile.
 11. Aflap deployment mechanism as claimed in claim 10 wherein the tracksystem has an “S” shaped profile.
 12. A flap deployment mechanism asclaimed in claim 9 wherein each of the at least two pairs of rollerscomprises an adjustment means for allowing the distance between the saidrollers disposed on opposite sides of the track to be adjusted.
 13. Aflap deployment mechanism as claimed in claim 12 wherein each of thepairs of rollers includes said adjustment means.
 14. A flap deploymentmechanism as claimed in claim 12 wherein the adjustment means is a camstyle adjuster.
 15. An aircraft wing having a flap deployment mechanismaccording to claim
 9. 16. An aircraft having a wing according to claim15.
 17. An aircraft flap arrangement in which the flap is deployablebetween a first stowed, or “cruise” position and a second deployedposition, the deployment movement including translational movement ofthe flap for which the flap is mounted on a carriage for rollingmovement along a track, the track having opposed rolling surfacesthereon and the carriage being movable along the track on at least twopairs of rollers, each pair of rollers having one roller running on eachopposed rolling surface and the rollers in each pair being linked by aconnecting means that maintains the roller in each pair of rollers at afixed distance apart in use, the connecting means is pivotally mountedto the carriage such that when the track is of multiple curvature theconnecting means pivots about the carriage maintaining both said rollersin each said pair of rollers in rolling contact with their respectivetrack rolling surface at all times, wherein each of the at least twopairs of rollers comprises an adjustment means to allow the distancebetween the said rollers disposed on opposite sides of the track to beadjusted.
 18. A flap deployment mechanism as claimed in claim 17 whereineach of the pairs of rollers comprises said adjustment means.
 19. A flapdeployment mechanism as claimed in claim 17 wherein the adjustment meansis a cam style adjuster.